The present invention relates to a salient pole having at least one flat coil for use in an electric motor, generator or the like, particularly a D.C. motor or generator, and to a process for the manufacture thereof.
Swiss Pat. No. 561,973 discloses an electric machine such as a motor or generator with salient poles. An exciter winding of the machine is made up of a number of disc-shaped flat conductors which are wound with flat wire and insulated from one another. The winding is impregnated with a curable composition which is subsequently cured. The individual coils of the excited winding have a single-layer winding of wire. The coils are held at a distance from one another and from the yoke and pole shoe of the machine. During manufacture, the coils can be placed over the pole core without the need for a holding device. An additional insulation layer is located between the coils and the pole core.
Coils of this type have a small height but, due to the small number of windings, are only useful in low voltage environments such as those associated with pilot exciter windings, for example. For the main poles of relatively small machines, where higher voltages are required and in which the number of windings is substantially greater due to the shorter length of winding, it is necessary to wind several layers of wire. As a result, the height of the winding is increased so that, consequently, larger poles must be employed. This in turn entails a larger machine casing and an increase in the axle height of the machine. Therefore, the previously described salient pole arrangement of the Swiss Patent can not be utilized for the windings of poles in which higher voltages are required, such as main poles, for example.
Round wires has not been suitable in the past for use in flat coils since adequate bonding could not be achieved. Moreover, cavities remain between the winding and the insulation which enable the insulation to detach itself or form bulges. A further problem is the wedge action which produces a pressure on the round wire windings. A force of about 100 kg/cm.sup.2 per layer can be generated.